As computer-based systems, appliances, automated teller machines (ATM), point of sale terminals and the like have become more prevalent in recent years, the ease of use of the human-machine interface is becoming more important. Such interfaces should operate intuitively and require little or no user training whereby they may be employed by virtually anyone. Many conventional user interface devices are available on the market, such as key boards, mouse, joysticks, and touch screens. One of the most intuitive and interactive interface devices known is the touch panel, which can be a touch screen or a touch pad. A touch screen includes a touch sensitive input panel and a display device, and provides a user with a machine interface through a panel sensitive to the user's touch and displaying content that the user “touches.” A conventional touch pad is a small planar rectangular pad, which can be installed near a display, on a computer, an automobile, ATM machines, and the like.
A conventional touch sensitive panel, for instance, usually has a smooth flat surface and uses sensors such as capacitive sensors and/or pressure sensors to sense locations being touched by a finger(s) and/or an object(s). A user, for example, presses a region or a point on a typical touch screen with a fingertip to emulate a button press and/or moves his or her finger on the panel according to the graphics displayed behind the panel on a display device.
A problem associated with a smooth flat surface touch screen is that it feels flat and smooth when a user touches the screen even though the image behind the surface shows an object such as a button. A conventional approach to compensate for flat and smooth touch feeling is to use haptic responses. To generate haptic responses that emulate an object such as a button, typical mechanical actuators or carriers, for instance, can be used to provide a virtual object or a barrier sensation.
A drawback associated with the conventional approach for generating haptic response is that it relies on global motion of a mechanical carrier attached to the touch screen. Another drawback associated is that it is often difficult to generate clear or crisp haptic responses.